The present invention relates to an electrical connector appropriate for use in transmitting high-frequency signals, and more particularly to a connector having terminals of substantially the same impedance.
In electronic applications that utilize high-frequency signals, it is desirable that the signal paths for such signals be optimized so as to control the resistance, capacitance and inductance which, in concert, affect the overall impedance of the signal paths. It is desirable to control the impedance of the signal path in order to prevent the degradation of the signals, especially high-frequency signals that traverse the signal path. Impedance may be easily controlled in electronic cables due to their construction, but it is more difficult to control in connectors because of the arrangement and structure of the conductive terminals of the connector. The spacing of the terminals must be taken into account, as well as their shape and also the dielectric material used for the connector housing.
FIG. 6 illustrates a conventional electric connector 50 that has a plurality of terminals 54 mounted in an insulative housing 51. The terminals are arranged in two parallel rows (shown as upper and lower) that extend in the direction (lengthwise) in which an opposing connector is inserted. These terminals 54 have contact portions (not shown) that are disposed in the connector housing 51 and tail portions 52 that extend out of the connector into position for surface mount soldering to a circuit board. The tails 52 of these terminals have different tail sections 52a and 52b because the upper and lower terminals are bent so as to form xe2x80x9cLxe2x80x9d-shaped, vertical leg and horizontal foot extensions. The horizontal foot extensions 53 are arranged to be flush with the bottom 51a of the insulative housing 51, thus permitting the horizontal foot extensions 53 to be used as soldering tails so that the terminals 54 may be soldered to opposing pods or traces on the circuit board.
As seen in FIG. 6, the vertical tail sections 52a and 52b of the upper and lower terminals differ in their lengths. The difference in these two lengths also effects the xe2x80x9celectricalxe2x80x9d length of the upper and lower paired terminals and so cause an adverse effect on high-frequency signals traveling on a transmission path through this connector. This conventional structure promotes a drastic change in the impedance of the terminals where they exit the connector.
In order to lessen the difference of the impedance change, attempts have been made to make the tail sections 52a and 52b of the upper and lower terminals have the same length. As shown in FIG. 7, the tail sections 52a and 52b of the upper and lower terminals are formed to have the same length. However, because the tail sections 52a and 52b are arranged in two parallel rows in the connector housing 51, they must be bent at four different locations as shown to compensate for the different vertical distances from the lower and upper levels. This provides terminal tail sections of the same electrical length, as seen in FIG. 7. This is shown in Japanese Laid-Open Patent Application No. 6-60946.
Although the same length of the terminal tail sections, 52a, 52b of such connectors causes no adverse effect on the high-frequency signals transmitted therethrough, the work required to bend and form these terminals is complicated, and there exists difficulty in putting all of the terminal tail ends in a coplanar relation relative to the surface of the printed circuit board. This is due to an increased amount of springback in each tail section caused by the numerous bends that are complex or right-angle bends. This type of structure lowers the reliability with which the terminal tail ends can be soldered to selected conductors in a printed circuit board.
Accordingly, the present invention is directed to a connector having an improved terminal tail structure that overcomes the aforementioned disadvantages and provides improved electrical characteristics to the connector.
It is therefore a general object of the present invention to provide a connector in which terminal tail portions have the same length and which have a structure that facilitates their attachment to a circuit board.
Another object of the present invention is to provide a connector having two rows of terminals arranged in upper and lower rows in a connector housing, in which the terminals of the two rows have same electrical length, and are formed in a manner that facilitate the bending of the terminal tail sections.
Yet another object of the present invention is to provide a connector for surface mount applications with improved impedance characteristics wherein the connector includes a plurality of conductive terminals having contact portions disposed in the connector housing, tail portions exiting from the housing, the tail and contact portions being interconnected by respective intermediate portions, the terminal tail and intermediate portions of the two rows of terminals having substantially the same electrical length and being oriented in opposing directions.
Still yet another object of the present invention is to provide a connector with improved electrical impedance characteristics in which the connector has a connector housing that houses a plurality of terminals, the terminals being arranged in at least two horizontal discrete rows of terminals, with the terminals further being arranged in discrete pairs of terminals between the two rows of terminals so that each discrete terminal in one row of terminals is associated with another discrete terminal in the other row of terminals, the discrete terminals of the one row having intermediate portions that slope downwardly to their tail portions and the discrete terminals of the other row of terminals having intermediate portions that slope upwardly to their tail portions, the opposing sloping portions of both terminal rows meeting their respective tail portions along a common line so that the electrical length of the terminals in one row is substantially the same as the terminals in the other row, and wherein the terminal intermediate portions have widths hat vary along their length so as to achieve an impedance along the intermediate portions of discrete pairs of terminals that is substantially the same as that of the tail portions of the discrete pairs of terminals.
To attain these objects, a connector is provided in accordance with the present invention in which the tail sections of two rows of terminals exit from the rear face of the connector housing and the associated intermediate portions of the terminals being bent obliquely relative to the rear face of the connector housing. A plurality of conductive terminals are mounted in the connector housing of the connector. The terminals include discrete pairs of terminals are arranged at least two distinct rows, preferably in two upper and lower rows with one terminal in the upper row being associated with a specific terminal in the lower terminal row.
The terminals extend longitudinally out of the connector housing. The intermediate portions of the upper row of terminals are bent downward from the rear face of the connector housing to where they meet their associated tail portions, and the tail sections of the lower row of terminals are bent upward from the rear face of the connector housing. The intermediate portions of the terminals of the upper and lower row meet with their associated tail portions along a common line. This bending arrangement of the intermediate portions of the terminals places the solder tail portions in a coplanar relationship with the bottom face of the connector housing, thereby permitting the solder tail portions to be soldered to selected conductors on a circuit board.
The small number of bends is easy to accomplish and it also reduces the total amount of springback in each terminal tail section. The solder tail portions may be arranged to be flush with the bottom of the connector housing thereby permitting required soldering to be performed on their surfaces. Alternatively, the solder tail portions may be vertical tails that can be inserted and soldered in selected through holes in a printed circuit board.
Each of the oblique, or sloping, portions of the terminal tail sections may have a width that preferably taper along their lengths toward their associated solder tail portions so that the surface area of the terminals is greater near the rear face of the connector housing which subsequently reduces along the length of the intermediate portions until they reach they associated tail portions. Thus, the upper and lower rows of terminals have a similar impedance as they exit out of the connector to thereby improve the transmitting performance for high-frequency signals.
These and other objects and advantages of the present invention will be clearly understood from the following detailed description.